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For forest-products-based industries, the significant benefits of preemptive arc-flash protection and online condition monitoring of electrical equipment are not well known. This paper provides a summary of the research surrounding the development and testing of new advanced sensor technologies for this purpose. This paper builds on the authors' initial research and their supporting publications providing more extensive and detailed field measurements supporting the preemptive detection of significant defects that can lead to an arc-flash event. The early detection of impending faults and the prediction of future arc-flash occurrences in medium voltage (MV) switchgears and motor control centers (MCCs) can be very beneficial. The development of new sensor technologies both for partial discharge measurement and thermal detection are discussed and evaluated. The two most common noncontact causes leading to an arc-flash event in MV switchgears and MCCs are insulation degradation and thermal stresses. This paper will highlight very detailed results measured under both of these conditions in laboratory and actual installed conditions. An effective signal processing method, which is used for extracting the essential indication data and for the integration of this system into existing protection programmable logic control or supervisory control and data acquisition (SCADA) systems, is outlined. [ABSTRACT FROM AUTHOR]

This paper evaluates the relationship between hazardous-rated electrical equipment, which is suitable for installation in Class I, Division 1 (Zone 1), or Division 2 (Zone 2) locations, and an arc-rated switchgear, which is designed to withstand the effects of an internal arcing fault. Using UL 1203 (Explosion-Proof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations), IEEE C37.20.7 (IEEE Guide for Testing Metal-Enclosed Switchgear Rated Up to 38 kV for Internal Arcing Faults), and the paper titled “Pressure Developed by Arcs,” this paper will explore the applicability of hazardous-rated equipment in the protection of personnel from an arc-flash hazard. [ABSTRACT FROM PUBLISHER]

This paper proposes a vector control strategy for independent control of two permanent-magnet synchronous motors (PMSMs) using a single four-leg inverter (4LI). An expanded two-arm modulation to obtain a balanced three-phase output voltage is described. This paper also proposes a method to compensate for the fluctuations in the neutral point voltage of two split capacitors in the dc link. The experimental results show that independent speed and position control of two PMSMs can be achieved using a single 4LI with the proposed vector control method. [ABSTRACT FROM AUTHOR]

The significant benefits of preemptive arc-flash protection and the online condition monitoring of electrical equipment are quite well known. Our continuing research focuses on the development of new advanced sensor technologies that are cost-effective, reliable, and efficient for the early detection of faults in order to predict impending arc-flash occurrences in mediumvoltage and low-voltage switchgear and controlgear. More extensive and detailed measurements regarding significant defects that lead to an arc-flash event have been completed since the original work in Part I was completed. A more detailed analysis of the results of this additional testing is presented in this paper. It has been documented that the two major noncontact causes that lead to an arc-flash event in switchgear are insulation degradation and thermal stresses. This paper covers the detailed measurement results under both of these conditions. New sensor technologies for both the partial discharge measurement and the thermal detection are introduced and evaluated. An effective signal processing technique, which is needed for extracting the essential indication of a developing fault, is also presented. Finally, this paper outlines how a preemptive arc detection system can be connected to protection, the programmable logic controller, or the supervisory control and data acquisition. [ABSTRACT FROM PUBLISHER]

This paper reviews factors that should be considered when determining maintenance intervals for overcurrent protective devices and switchgear. Performing maintenance on a regularly scheduled basis is good, but how do you determine those intervals? This paper provides some guidance on that question. [ABSTRACT FROM AUTHOR]

This paper will present a new approach that is advantageous to medium-voltage (MV) distribution design configurations for large industrial and power distribution system configurations [specifically main-tie-main (MTM)] for large industrial and power station installations. Sixty years of traditional low-cost design approaches (typical MTM and operated with open tiebreaker) are re-evaluated to demonstrate that traditional low capital cost design may miss improvement opportunities. Those opportunities can be major capital expenditure reduction, power quality improvement, MV motor soft starter deletion, and improved system stability to name a few. Many designers may not have considered the component interrelationships and/or their tradeoffs when in an integrated system. The designer and/or user should consider the advantages of higher short-circuit capacity (SCC) systems by integrating fault current limiters and MV switchgear. Utilizing higher SCC systems permits power system designer optimization opportunities not possible before using conventional design methods. This paper will provide documentation of substantial savings of capital investment and energy under higher SCC conditions. The savings in one system component will offset another's increased cost. An obvious benefit of stiffer systems is ease of direct-on-line starting of large motor-driven compressor trains. The future need for motor soft starters minimizing system impact will be challenged. This paper may change fundamental system design methodology for system designers by removing several performance tradeoffs. This paper, in its original version, was previously presented at the 2010 IEEE/IAS/Petroleum Chemical Industry Conference. It was expanded with new sections for the 2017 IEEE/Industry Applications Society (IAS)/Pulp, Paper Forestry Industries Conference to include pre-emptive prefault adjustable power quality and multisourced networked power systems. [ABSTRACT FROM PUBLISHER]

The major types of slowly developing faults, which can lead to arc faults in switchgear and controlgear, such as partial discharge, arcing, and heating due to poor connections, can now be successfully detected and monitored. In parts I and II of this paper series, a detailed review of the immediate causes of arc faults, along with an overview of preignition and postignition methods for its mitigation, was presented. Various hybrid nonintrusive sensors were developed in the laboratory to implement preignition detection techniques. The major types of slowly developing electrical faults were created in the laboratory, and the sensors were employed to evaluate their performance along with an effective signal processing technique. Part III of the work is based on the successful performance of the sensors outside of laboratory conditions. Hybrid sensors have been installed in a real-world application, i.e., switchgear located in substations. This paper presents interesting results about this practical application and includes valuable discussion on the performance evaluation of different sensors, which further justifies the usefulness of the new sensors for online condition monitoring of switchgear, controlgear, and cable termination boxes. The implementation of this technology in industry may provide promising results in avoiding major accidents such as arc-flash in the switchgear and controlgear. [ABSTRACT FROM AUTHOR]

Multioutput converters with single input source are currently studied as an alternative to conventional dc–dc topologies in order to improve power density in low-power multiload applications. This paper reviews three different ways in which a boost topology can be customized to supply multiple outputs. The first way uses a charge-sharing approach using individual switches to distribute inductor energy to different capacitors. The second method of creating a multiport converter (MPC) combines two converters with similar front end to generate two outputs using only one controlled switch. Using this method, a boost converter can be combined with single–ended primary–inductor converter (SEPIC), Cuk, and current source converter topologies. The third method uses time multiplexing of switches to produce two regulated ports and is referred to as switched-boost action. This method uses relatively less number of switches and allows regulation and control of all the outputs. Practical utility of switched-boost action based MPC is reported in this paper. This switched-boost MPC is applied to a renewable power converter system to interface a solar panel, a battery, and home loads to produce a 12-V and a 48-V bus. The 12-V bus is interfaced to battery and capable of optimally charging the battery in constant current–constant voltage (CC-CV) mode. The converter is demonstrated to operate with solar panel as it supplies a 12-V battery and a 48-V load bus. When the solar power is not available, the converter automatically goes into a mode in which the 12-V battery supplies the loads on the 48-V bus. [ABSTRACT FROM AUTHOR]

This paper proposes a single-stage three-phase-to-single-phase current-fed high step-up ac–dc matrix converter. The proposed converter inserts a boost-type matrix converter, which is formed by three boost inductors and six bidirectional switches, between a three-phase ac source and a Cockcroft–Walton voltage multiplier (CWVM). By using this topology associated with power factor correction technique, the proposed converter not only achieves almost unity power factor and sinusoidal input currents with low distortion but also obtains high voltage gain at the output end. Moreover, the matrix converter generates an adjustable-frequency and adjustable-amplitude current, which injects into the CWVM to regulate the dc output voltage and smooth its ripple. With this flexible injection current, the performance of the proposed converter is superior to the conventional CWVM, which is usually energized by a single-phase ac source. The operation principle, control strategy, and design considerations of the proposed converter are detailed in this paper. Finally, simulation and experimental results demonstrate the claims and validity of the proposed converter. [ABSTRACT FROM PUBLISHER]

This paper demonstrates the impacts of an electronically triggered fault current limiter (ET-FCL) on typical single-ended and main–tie–main (MTM) medium-voltage switchgear arrangements. The fast acting (less than 1 ms) ET-FCL described in this paper effectively opens the normally closed tie connection between two mains, thereby disconnecting one of the sources to the fault. An ultrafast opening of the tie connection simplifies protection coordination by not having to coordinate the main breaker relay with the tie breaker relay at maximum fault levels. System benefits include the following: significantly lower arc flash energy for downstream faults, faster backup clearing times for a feeder relay/breaker failure, reduction of motor starter dropouts due to fault-produced voltage dips, improved system stability, improvement in utility's CAIDI reliability index, reduced stress on switchgear breakers, and overall lower capital costs on new construction (switchgear, cables, etc.). This paper demonstrates relay setting changes on typical single-ended and MTM arrangement with and without applying the ET-FCL. Impacts on incident energy reduction, backup clearing times, dynamic system stability, and voltage dips will be discussed. [ABSTRACT FROM PUBLISHER]

In this paper, an overview of the main motor features influencing the protection devices settings is presented, pointing out key differences between three-phase direct-on-line (DOL) motors of different efficiency classes. The results of experimental tests and simulations are presented and discussed in the scope of the motor protection against overload, short-circuit, current unbalance, and locked-rotor conditions, for 7.5-kW, four-pole, IE2- and IE3-class squirrel-cage induction motors (SCIMs) and for IE4-class line-start permanent-magnet motors (LSPMs), offering important data related to their electrical and thermal behaviors. Two commercial digital thermal-magnetic motor protection devices, whose thermal models were designed for IE1- and IE2-class motors, are evaluated in terms of operation effectiveness in the tested motors. This paper is important for industry due to the significant penetration of IE3-class induction motors, as well as to the recent introduction into the market of IE4-class induction motors and LSPMs. [ABSTRACT FROM PUBLISHER]

Oversizing electrical distribution equipment is a concern in industrial facilities. It adds cost and can increase fault levels. IEEE Std 141-1993 provides guidelines on how to size electrical equipment, but at the early stage of the project, when the equipment is being purchased, much of the process information necessary to properly size the equipment is preliminary at best. In addition, much is left to the discretion of the individual design engineer, who is often not an employee of the facility's eventual owner and, therefore, may have no incentive to reduce equipment size. In fact, depending upon the contractual relationship and due to the preliminary data, compressed schedule, and long delivery, design engineers tend to oversize the equipment. This paper describes an approach for establishing a load-based upper size limit to control oversizing of electrical equipment. This paper will demonstrate that establishing this upper limit can effectively control oversizing of the electrical equipment with information available at the early stage of the project. The resulting safety and economic benefits of the properly sized electrical equipment cascade throughout the power system. [ABSTRACT FROM AUTHOR]

This paper proposes an adaptive power management strategy for photovoltaic (PV) generation units in a standalone microgrid. In existing microgrid configurations, the PV units are controlled using droop control technique, which ensures load sharing among the distributed generation (DG) inverters. However, the intermittency in power generation of PV-based DG poses many challenges to the standalone operation of a microgrid, the ineffective volt-ampere (VA) utilization being one among them. This paper proposes an adaptive droop control, which enables the maximum utilization of the VA rating of the interfacing inverter in a PV/battery hybrid system. With the proposed technique, as the generation goes down, the DG inverter is controlled to support the reactive power demand of the load, thereby utilizing the rating of the inverter switches effectively. The applicability of the proposed adaptive control method is analyzed using detailed simulation and real-time hardware-in-loop studies. [ABSTRACT FROM AUTHOR]

Finite state model predictive control (MPC) has been recently applied to several converter topologies, as it can provide many advantages over other MPC techniques. The advantages of MPC include fast dynamics, multitarget control capability, and relatively easy implementation on digital control platforms. However, its inherent variable switching frequency and lower steady-state waveform quality with respect to standard control, which includes an appropriate modulation technique, represent a limitation to its applicability. Modulated model predictive control (M2 PC) combines all the advantages of MPC with the fixed switching frequency characteristic of pulse-width modulation algorithms. The work presented in this paper focuses on the indirect matrix converter (IMC), where the tight coupling between rectifier stage and inverter stage has to be taken into account in the M2PC design. This paper proposes an M2PC solution, suitable for IMC, with a switching pattern that emulates the desired waveform quality features of space vector modulation for matrix converters. The switching sequences of the rectifier stage and inverter stage are rearranged in order to always achieve zero-current switching on the rectifier stage, thus simplifying the current commutation strategy. [ABSTRACT FROM AUTHOR]

A method for the seamless transition of three-phase inverters switched between grid-tied and stand-alone modes of operation is presented in this paper. In this method, only the inverter current and voltage sensors are utilized, and no control over the grid-side static transfer switch is needed. The presented method contains two strategies for grid-tied-to-stand-alone and stand-alone-to-grid-tied transitions. In the stand-alone-to-grid-tied transition strategy, a novel algorithm is presented for estimating the grid angle nearly instantaneously, which allows the three-phase inverter to respond very quickly if the grid and point-of-common-coupling voltages are out of phase. This fast response allows the inverter to effectively eliminate the transient overcurrent that would normally occur if it was connected to the grid without first being synchronized. The fast response also allows the inverter to return to normal operation very quickly after such an event. The strategy for the seamless transition from grid-tied to stand-alone mode is also presented. These strategies have been verified through experiments, and the results are presented in this paper. [ABSTRACT FROM PUBLISHER]

This paper presents single- to three-phase dc-link converters with a reduced number of controlled switches for either usual or reduced currents in switches of the rectifier. A suitable model and a control strategy, including a synchronization approach, are developed to obtain the maximum dc-link voltage utilization. Such a synchronization method, associated with the pulse-width-modulated generation signal, forces the input current to have the same phase angle as the input voltage. The main advantage of the proposed converters along with the synchronization method is the reduction of the zero-crossing distortion normally caused by the use of diodes. Simulated and experimental results are presented to confirm the validity of the theoretical expectations. [ABSTRACT FROM PUBLISHER]

Power quality metering is a situation that often does not afford the safety of deenergizing equipment before connecting probes; this is especially true for continuous processes such as those found in refineries. In this situation, a connection to energized equipment may be more common. When potential and current transformers are present in switchgear, it is usually desirable to make the probe connections to the secondary of these transformers. Generally, these connections are made in switchgear metering compartments, which are presumed to have low arc-flash risk due to the limited exposure to energized power conductors. Often in these situations only shock hazard is considered and arc-flash hazard is not, but is it safe to assume there is no arc-flash hazard? The NFPA 70E-2015 Standard states that opening doors to expose bare energized parts requires arc-flash personal protective equipment (PPE). The standard also states that work on control circuits with exposed energized parts greater than 120 V requires arc-flash PPE. Therefore, according to the NFPA 70E, in a control cabinet containing, for example, voltage transformers with exposed primary terminals above 120 V, an arc-flash hazard exists and arc-flash PPE is required. However, the question remains, what level is the hazard and how should it be assessed? This paper will evaluate arc-flash energy in metering compartments, determine if arc-flash hazard should be a legitimate concern when working in energized metering compartments, and improve overall awareness when working in these situations. [ABSTRACT FROM PUBLISHER]

This paper shows a winding design consideration of a 50-kW switched-reluctance motor (SRM) for hybrid-electric-vehicle (HEV) applications. Increasing the number of turns in stator windings is effective in reducing the maximum current; thus, the inverter current rating is reduced. However, motor output power falls significantly at high speed because of the increased back electromotive force. Continuous current operation can enhance output power at high rotational speed. In this operation, phase current is increased, and hence, the motor output power is maintained at high rotational speed. However, continuous current operation results in a decrease in efficiency. Thus, there is a tradeoff in selecting the number of series turns. In this paper, two SRMs are constructed with the same dimensions, and their performance results, i.e., torque and efficiency ranges, are compared with those of the automotive industry standard interior-permanent-magnet motor for HEV applications. [ABSTRACT FROM AUTHOR]

Common-mode voltage (CMV) in voltage-source inverters (VSIs) has been well defined and is frequently referred to in the literature. While often referred to, there is no real consistency with respect to how the CMV properties of an individual modulation scheme are evaluated, lacking tools to assess the relative merits or disadvantages of a certain topology or modification of a control scheme. The way that it is analyzed is still mostly a matter of the different authors' foci. In this paper, we propose a metric for the analysis of the CMV, aiming to fill the aforementioned gap. Thereby, the CMV in VSIs is quantified by the number of possible levels and the step sizes between different levels, as well as the respective frequencies of occurrence. The first two are given by the number of levels and the number of phases of the inverter. Depending on the modulation (control) schemes, all possibly available levels or a few of these levels are present in the CMV. We illustrate the use of the tool by applying it to thoroughly study the CMV properties intrinsic to the topologies of multilevel multiphase single- as well as double-ended diode-clamped VSI drive systems. As part of this analysis, we uncover new relationships concerning the existence of zero CMV level. Furthermore, we exemplarily apply the developed tool to the assessment of the CMV properties of selected pulse width modulation (PWM) control schemes and translate the findings into an interpretation of the endangerment of a given drive to suffer damage from inverter-induced bearing currents. The theoretical findings are supported by measurements. This paper also reviews the literature on CMV in multilevel multiphase VSI systems. With the proposed metric in mind, the CMV being mostly discussed as an element of different foci becomes even clearer, confirming again the need for the development of such a tool. [ABSTRACT FROM AUTHOR]

The switched shunting resistor circuit is a classical and practical passive equalization scheme that nevertheless suffers from the voltage imbalance after the charging process. It results from the discrepancy of the shunting resistor and the physical characteristics of supercapacitor (SC) cells. In this paper, the distributed voltage equalization control strategies with the proportional-integral (PI) observer for the switched shunting resistor circuit are analyzed and compared. First, the charging and equalizing system is modeled as the switched system and the system observability is proved. The decentralized control and consensus control are analyzed and their shortages are presented. Then, the leader–follower cooperative control is proposed to improve the charging time while keeping the equalization performance. Meanwhile, the PI observer is designed to estimate the internal capacitance voltage of an SC precisely to avoid the effect of equal series resistance. The control convergence is proved by using the Lyapunov stability and switched system theory. The experimental results show that the proposed method has much superiority and wide applicability than the existing methods for equalizing voltages of SCs. [ABSTRACT FROM AUTHOR]

Renforth et al. in 2017 present a novel online partial discharge (OLPD) high-voltage (HV) insulation condition monitoring (CM) solution to monitor complete HV networks in petrochemical and other critical industry facilities. Continuous, 24/7 OLPD insulation monitoring of in-service cables, switchgear, transformers, and rotating machines operating at 3000 V and above provides operators with an early warning against incipient HV insulation faults that manifest themselves through high PD activity. Knowledge of the type, severity, and source of any site(s) of PD across the HV network (including remotely connected plant such as Ex/ATEX HV motors located in hazardous gas zones) enables pinpointed preventative maintenance interventions to be made to the HV insulation system during planned maintenance turnarounds to avoid unplanned outages. To monitor a complete HV network, OLPD sensors and monitoring nodes are distributed at strategic locations across the network. The CM data from the distributed nodes are passed via Ethernet/LAN to a partial discharge monitoring server (PDMS) located at the control center of the facility with a secure internet connection. The PDMS operates an advanced OLPD monitoring database for the logging, display, benchmarking, trending, and visualization of the PD monitoring data on a graphical user interface. The insulation condition criticality (from 0% to 100%) of each phase of all of the individual HV plant items monitored is presented on a series of mimic screens of the HV network single-line diagram. This paper concludes with a case study of a complete HV network OLPD monitoring design solution implemented at a large, crude-oil processing facility in Eurasia. [ABSTRACT FROM AUTHOR]

This paper discusses the arc flash ramifications associated with the design and selection of medium-voltage switchgear. Three case studies are presented to demonstrate the impact of performing arc flash hazard analysis on the proposed and/or existing medium-voltage installation at the design stage. This paper proposes the following: 1) changes in the National Electrical Code, Article 110.16, to provide mandatory requirements for a) performing arc flash analysis at the design stage and b) placement of warning labels on switchgear to warn qualified persons of potential arc flash hazards and 2) a need to promulgate regulations requiring a utility company to notify its customers of changes in a) the available fault duty at the point of common coupling with a customer's facility and b) utility upstream protective device settings. [ABSTRACT FROM AUTHOR]

DC microgrid systems with hybrid energy resources are of significant interest in shipboard and spacecraft applications. In such a system, coordinated operation of circuit breakers (CBs) and disconnecting switches (DSs) can rapidly isolate short-circuit faults and restore the system very fast. In this paper, we investigate a new protection scheme for a Multi-Bus dc systems based on an event classification approach. The proposed protection scheme transfers less data when compared with commonly used data-based protection methods and does not require high-speed communication and synchronization. The results show that the developed protection scheme is able to identify the type of fault accurately, isolate the faulted area, and restore the system very quickly while maintaining continuous power to the loads. [ABSTRACT FROM PUBLISHER]

Parallel ac-link universal power converters are a relatively new class of power converters that can be configured as dc–dc, dc–ac, ac–dc, and ac–ac. These converters are extensions of a buck–boost converter in which the current of the inductor is alternating and the input and output can have any number of phases with any forms, voltage amplitude, or frequency. By placing a small capacitor in parallel with the link inductor, all the switches can benefit from soft switching. The main limitation of the parallel ac-link universal power converter is its large number of switches. A three-phase ac–ac configuration requires 24 unidirectional switches. This paper proposes two topologies based on the parallel ac-link universal power converters that significantly reduce the number of switches. One of the proposed topologies reduces the number of switches in a three-phase ac–ac configuration to 16. The other topology reduces the number of switches to 10. The latter can offer galvanic isolation with only a single-phase high-frequency transformer. This paper presents the principles of the operation of the proposed topologies and evaluates them through simulation and experiments. [ABSTRACT FROM AUTHOR]

This paper presents two power-generation systems with a two-phase permanent-magnet (PM) synchronous machine associated with a rectifier with small number of controlled switches. The topologies are conceived with the purpose of converting wind energy into electrical energy for low-power applications, providing an enormous potential to be used in urban areas. They can be used in applications connected to the grid or in the stand-alone mode or feeding a microgrid. Compared with some three-phase generation systems with reduced number of controlled switches, the proposed topologies permit obtaining sinusoidal controlled machine currents, reducing dc-link voltage and providing $dq$ currents with low harmonic distortion. [ABSTRACT FROM AUTHOR]

A digital dead-beat current controller for voltage source converters is presented in this paper. The control structure is specified in a digital hardware description language, synthesized, and deployed on a field-programmable gate array chip. By updating, with negligible computation delay, the duty cycle twice in a switching period, the reference current error is nulled in half a modulation period, so that the controller's small-signal bandwidth is maximized. In addition, due to a simple transient detection circuit, the large-signal response delay is reduced to a small fraction of the modulation period, which is determined by the chosen current signal oversampling rate. The controller can effectively support different voltage-source inverter applications, such as active filters, uninterruptible power supplies, microgrid distributed energy resource controllers, and dc–dc converter applications, including interface converters for renewable energy sources, laboratory battery chargers, and electronic welding machines. [ABSTRACT FROM AUTHOR]

The architecture of a mission critical power system has to be designed with structures that allow the simultaneous operation of multiple sources (architecture efficiency). Opportunely organized, the business continuity management will project its program and take actions on the sources. Complete control of the system is necessary for all operating occurrences in an electrical power system. Complexity requires that “safe sets” of operating procedures have to be identified, selected, and authorized, as adopting the Parise program. A Human Competent Reaction has to guarantee the operation efficiency as providing decision-making in emergency statuses. The paper deals with a sample case of a system with multiple sources applying the micro approach of the “flock” logic that consists in managing exclusively the adjacencies of each node. The adoption of mechanical locking tools assists the switching procedures. [ABSTRACT FROM AUTHOR]

An application-oriented integration concept for a half-bridge switch assembly has been developed based on the latest generation 70- \mu\m-thin insulated gate bipolar transistors and diodes, which are rated at 600 V/200 A. This paper addresses the design and reliability of the assembly, with a fully bondwireless approach using cylindrical copper bumps. Advanced numerical structural simulation techniques are also applied to assess the influence of interconnect characteristics (material, size, and shape) and try to determine an optimum solution for reducing the stress and creep strain development in the solder joint. Preliminary experimental tests of the power module are also carried out at different switching frequency and loads to prove the validity of the proposed solution in terms of electromagnetic performance. [ABSTRACT FROM AUTHOR]

This paper proposes an offline single-stage light-emitting diode (LED) driver based on a novel approach to reduce low-frequency ripple in LED arrays supplied from mains, while assuring high input power factor (PF). The proposal employs a series resonant dc–dc converter integrated into a bridgeless boost power factor correction (PFC) stage. The resonant stage works to reduce the low-frequency ripple transmitted from the output of the PFC stage to the LEDs with only small power losses. This solution achieves three main goals: 1) reduction of the bulk capacitance used at the dc bus, allowing for the use of long-life film capacitors; 2) increase in the overall efficiency of the LED driver owing to the low switching and conduction losses in the shared switching network; and 3) assuring high input PF. Experimental results of a driver without electrolytic capacitors for a 100-W street lighting LED luminaire are presented, showing overall efficiency in excess of 92%, input PF greater than 0.97, and line current harmonic content in compliance with the IEC 61000-3-2 standard. [ABSTRACT FROM AUTHOR]

An open-winding permanent-magnet synchronous generator (PMSG) system with the integration of fully controlled and uncontrolled converter is investigated in this paper, in which half the amount of controllable power switches are needed compared with the conventional open winding system fed by two voltage source converters. The voltage space vector of open winding PMSG is modulated by controlled converter, which will be integrated with the voltage vector by uncontrolled converter to implement the operation of open winding PMSG. In order to analyze and compare the operation capability on the different dc voltage ratios, the available modulation range of the open winding PMSG is analyzed in detail. Moreover, unity power factor control is proposed as the optimized control method to achieve the maximum modulation index. Finally, a 1-kW experimental setup is built to validate the theoretical investigation on the open winding PMSG system. [ABSTRACT FROM AUTHOR]

In this paper, a switched reluctance motor (SRM) with phase windings similar to an autotransformer is presented. The new winding structure allows for fast demagnetization. This enhances the machine performance at high speeds. During demagnetization, the dc bus voltage is applied to a portion of the phase winding, and accordingly a higher negative demagnetization voltage/turn is applied. This results in the faster discharge of the phase excitation currents. The power electronic converter configuration is modified to facilitate the new winding topology. However, the number of switches is the same as a conventional half-bridge converter used in SRMs. The proposed SRM drive with the modified winding configuration is verified through finite element analysis based circuit simulations and experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage light-emitting diode (LED) driver based on a bridgeless power factor correction (PFC) converter and a half-bridge CLCL resonant converter for street lighting applications. The proposed single-stage topology integrates the PFC converter and the CLCL resonant converter by sharing active power switches. The bridgeless PFC converter adopts two buck–boost circuits operating in discontinuous-conduction mode to achieve input-current shaping. It uses two diodes instead of a rectifier bridge to reduce the power loss caused by the diodes. Owing to its superior soft-switching characteristics, the CLCL resonant converter is used. The proposed LED driver has superior features, such as high efficiency, near unity power factor, low total harmonic distortion, and relatively few diodes. A 100-W lab prototype is successfully implemented, and the experimental results verify the effectiveness and feasibility of the proposed LED driver. [ABSTRACT FROM AUTHOR]

This paper proposes a real-time hybrid fuzzy bang–bang (BB) controller with switching function, in order to implement a full nonlinear control law. The controller consists of a fuzzy-BB controller in parallel with a BB controller while the system is in operation. In order to circumvent the shortcomings of fuzzy-BB and BB-based controllers, a hybrid fuzzy-BB controller is proposed, in which the output can be either the outputs of the two, i.e., the fuzzy-BB or BB units that are being switched as per the absolute error signal. Normally, the BB controller operates in general; the fuzzy-BB controller is activated when the drive system experiences oscillatory behavior. The choice between the fuzzy-BB and BB controllers is based on a set of simple if–then rules; the overshoot and the oscillatory behavior have to be detected by the absolute errors. Trajectory tracking of nonlinear motor drives in position mode serves as a test bed for the control law, and a real-time experiment allows for the assessment of its practical applicability. The hybrid fuzzy-BB controller has been implemented on hardware with a dSPACE digital signal processor, and it is observed that the performance of the controlled brushless dc motor drive with the hybrid fuzzy-BB controller is assuring. Noticeably, experimental results demonstrate that the proposed controller is capable of significantly cultivating the motor performance under random disturbance and different loading conditions. [ABSTRACT FROM PUBLISHER]

This paper proposes and investigates a multilevel ac six-phase motor drive. The system is composed of five isolated three-leg voltage source inverters feeding the open-end windings of an asymmetrical six-phase induction motor (SPIM), which is adequate to generate multilevel voltages for high-power systems with voltage rating restrictions. A simple space vector pulse-width modulation (PWM) based on three similar individual planes and its implementation by means of equivalent level-shifted PWM are presented. A space vector pattern with a high number of voltage vectors redundancies is obtained. These redundancies and the application sequence of the voltage vectors are selected to minimize the amount of changes in the switching states and to decrease the harmonic distortion of the generated voltages. The vector pattern of this optimal modulation is obtained by analyzing only one plane and applied in the same way to the three planes as if they were independent. The developed PWM techniques have low computational complexity and are suitable for low-cost hardware implementations. Simulation results are used to compare the proposed topology with a conventional configuration in terms of harmonic distortion and semiconductor losses. Experimental results demonstrate the feasibility of the proposed drive system. [ABSTRACT FROM AUTHOR]

Usually, the high-gain high-efficiency dc–dc converters consist of many passive components, which increases the order of the system. As the order increases, system modeling and control become more complex. Thus, there is a need for the simplification of the small signal modeling process of such converters. This paper presents a generalized small signal model and equivalent circuit for an $n$ th-order coupled-inductor-based high-voltage gain converters (CIHVGC) that can be conveniently used for the control design. The state variable representation of a generalized coupled inductor with p windings is included. A simplified step by step procedure to obtain small signal model using visual inspection is presented. Analysis is included and verified using simulations and experiments for the output voltage regulation of high-voltage gain converters. The usefulness and versatility of the proposed model is verified with three examples of high gain converters belonging to the CIHVGC family. All the analytical, simulation, and experimental details of this paper are presented. [ABSTRACT FROM AUTHOR]

A zero-current switching full-bridge isolated dc/dc converter based on a semiresonant L-C cell has been developed in this paper. With respect to the classical full-bridge configuration, no additional switches are required, thus by preserving its simplicity and robustness. The proposed architecture allows achieving zero-current switching at both primary and secondary sides. A 50-kW prototype has been developed and tested in different operating conditions. The experimental results are in agreement with the simulations by confirming the goodness of the proposed solution. Efficiency up to 97% at full load operating condition has been reached in the laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper presents a case study of a medium-voltage three-phase capacitor bank (CB) energization, based on an unsynchronized switching scheme using three independent pole vacuum switches simultaneously commanded. The motivations are cost reduction and simplification of the switching scheme. The maximum current and voltage peaks during transients caused by connection of CB with three independent pole switches or a three-phase mechanically coupled switch are compared. A probabilistic assessment for the overcurrents and overvoltages based on Monte Carlo simulation is also performed. The obtained results show that three single-phase unsynchronized switches could be used in a CB, with good transitory response. [ABSTRACT FROM PUBLISHER]

This paper presents the experimental results of the independent drive characteristics of two three-phase induction motors (IMs) fed by a four-leg inverter (FLI). The FLI is a single inverter that can drive two three-phase ac motors independently. The inverter consists of four legs and two capacitors connected in a series. The U and V phases of both motors are connected in each leg, respectively, whereas the W phase of both motors is connected in the neutral point of two-sprit capacitors. The pulsewidth modulation technique in three-phase voltage source inverter is not directly applicable for the FLI because only two phases must be modulated. Then, this paper also analyzes about the neutral point potential of two-sprit capacitors and inverter output voltage. Next, the modulation technique in the FLI is also shown. The experimental results demonstrate the characteristics of two IM independent drives and the validity of those analytic results. [ABSTRACT FROM AUTHOR]

The conventional current-source inverter has two major problems: unidirectional power flow and voltage boost operation, which make it impossible to be used in many applications, such as hybrid electric vehicles and general-purpose variable-speed motor drives. Z-source inverters (ZSIs) can solve both problems. Quasi-ZSIs (qZSIs) were recently proposed as an important improvement to traditional ZSIs. Besides the advantages inherited from ZSIs, qZSIs also have several of their own merits. This paper presents a comprehensive study on the new features of current-fed qZSI, including the advantageous buck–boost function, improved reliability, reduced passive component ratings, and unique regeneration capability. The current-fed qZSIs are bidirectional with an additional diode, unlike the voltage-fed ZSI that needs a switch to achieve bidirectional power flow. A modified space vector pulse-width-modulation method is proposed, and the available operating regions for motoring and regeneration operation are analyzed in this paper. Since the current-fed qZSI has the same operation as the current-fed ZSI, many results of this paper are also applicable to the current-fed ZSI. A reverse-blocking insulated-gate bipolar-transistor-based current-fed qZSI prototype was developed in the laboratory. Simulation and experimental results are shown to verify the theoretical analysis. [ABSTRACT FROM PUBLISHER]

In this paper, a new design methodology for low-voltage electromagnetic energy harvesting systems consisting of a microgenerator and power processing circuit is introduced. In the first section of this paper, a simple topology for a resonance-based electromagnetic generator is presented. The microgenerator is capable of producing a voltage of a few hundred millivolts. Since traditional two-stage power conversion schemes cannot be used for such a low ac voltage, a suitable single-stage ac–dc converter is utilized for power processing. The converter boosts the low ac voltage to a nominal dc voltage required by electronic devices. As a part of integrated design, the coil of the microgenerator is fabricated such that it can be utilized both for electromagnetic induction and power processing. Such an arrangement improves efficiency and makes the system compact. The converter is controlled to regulate the output voltage under varying input or load conditions. Simulation and experimental results are presented to validate the operation of the proposed converter with a low-voltage microgenerator. [ABSTRACT FROM PUBLISHER]

Switching transients associated with circuit breakers have been observed for many years. Recently, this phenomenon has been attributed to a significant number of transformer failures involving primary circuit-breaker switching. These transformer failures had common contributing factors such as the following: 1) primary vacuum or SF-6 breaker; 2) short cable or bus connection to transformer; and 3) application involving dry-type or cast-coil transformers and some liquid-filled ones. This paper will review these recent transformer failures due to primary circuit-breaker switching transients to show the severity of damage caused by the voltage surge and discuss the common contributing factors. Next, switching transient simulations in the electromagnetic transients program will give case studies which illustrate how breaker characteristics of current chopping and restrike combine with critical circuit characteristics to cause transformer failure. Design and installation considerations will be addressed, particularly the challenges of retrofitting a snubber to an existing facility with limited space. Finally, several techniques and equipment that have proven to successfully mitigate the breaker switching transients will be presented, including surge arresters, surge capacitors, snubbers, and these in combination. [ABSTRACT FROM PUBLISHER]

This paper presents an alternative approach to thyristor-controlled series capacitor (TCSC) performance analysis. The approach is to interface a small-scale physical model of the TCSC with a classic physical power system simulation laboratory. The platform is capable of investigating the operation, protection, and control strategies of TCSCs. Furthermore, it can be used to investigate complex phenomena such as the breakdown of metal oxide varistors. Such phenomena are very difficult, if not impossible, to investigate using digital simulation methods. [ABSTRACT FROM AUTHOR]

In electrical installations, each working zone and each source node present a kit of operating instructions as a logic gene. Previous papers have introduced a new approach and a language of a ternary code for operational procedures (Parise program). This paper deals with some comments on definitions and the syntax of the operational language. The same status of switching defines working zones or nodes by double operating value, free value, and packed value, thereby discriminating between decision and execution, and executed act from verification. The recommended command is a double click. The instructions have to be assembled like in a genetic cryptogram in the context of an electrical power system and of its architecture and constitution. They describe the complete and reversible evolution of the operational procedures for safe transition from a one set of switching configuration to another (waves of safe sets). Transitions maps are introduced to assist in the elaboration of operational procedures and to help the training of operators, their competence, and performance. These maps are specialized for the operational procedures more than the Karnaugh maps of digital electronics. On the basis of the logic gates, the basic equivalent mechanical connectives are defined to guide the operational procedures. A switching simulator based on electronic gates can be very useful for verifying the effects of any set of switching operations, adopting for commands the double click. [ABSTRACT FROM AUTHOR]

This paper will review some of the problems in controlling electrical motive energy on an industrial machine during operational and maintenance intervention and will present an update on the proposed solutions. The problem and the proposed initial solutions were presented in a first paper, "Electrical Safety Related Isolation on Industrial Machines with Multiple Entry Points." Originally, this paper was presented under the title "Equipment Used for Electrical Safety-Related Isolation on Industrial Machines by William E. Anderson, P.E." at the 2003 Industrial and Commercial Power Systems (I & CPS) Department Conference in St. Louis, MO, Paper "I & CPS 03-20." [ABSTRACT FROM AUTHOR]

This paper discusses the potential of a transformer-less STATic synchronous COMpensator (STATCOM) intended for installation on the 6.6-kV industrial and utility distribution systems. The STATCOM consists of a five-level diode-clamped pulsewidth-modulation converter rated at 1 MVA and a voltage-balancing circuit rated at 6 kVA. Moreover, this paper designs, constructs, and tests a 200-V 10-kVA STATCOM based on a five-level converter with a carrier frequency of 3 kHz and a voltage-balancing circuit with a switching frequency of 3 kHs. The STATCOM and its experimental waveforms verify the viability and effectiveness of the 6.6-kV transformerless STATCOM. [ABSTRACT FROM AUTHOR]

An arc fault is the discharge of electricity through the air between two conductors creating large quantities of heat and light. It is widely accepted that there are many variables which affect the behavior of an arc in real switchboards, and thus, understanding the phenomena is difficult. This paper is based upon the results of several years of arc testing with circuits from 155 Vdc to three-phase 450 Vac and at power levels from tens of kilowatts to several megawatts. The goals of the testing were to understand the general behavior of arcing faults in low-voltage switchboards—well enough to predict the motion of arcs—and to design electronic monitoring systems that are capable of protecting switchboards against arcs. This paper will focus on the arc behavior, whereas our other papers will discuss its implications upon forensic investigations and upon the arc-fault protective systems. [ABSTRACT FROM AUTHOR]

This paper presents an active-clamp push-pull converter for battery sourcing applications. A pair of auxiliary switches, resonant inductors, and clamping capacitors is added to the primary side of the transformer to clamp voltage spike and recycle the energy trapped in the leakage inductors. In the proposed active-clamp push-pull converter, since both main and auxiliary switches can be turned ON with zero-voltage switching, switching loss can be reduced and conversion efficiency therefore can be improved significantly. Furthermore, the proposed converter can eliminate potential flux-imbalance problems existing in the conventional push-pull converter. In this paper, a 1 kW active-clamp push-pull converter was implemented, from which experimental results have shown that efficiency improvement and surge suppression can be achieved effectively. It is relatively feasible for applications to battery sourcing converters. [ABSTRACT FROM AUTHOR]

A modular quasi-resonant bidirectional dc–dc converter composed of half-bridge gallium nitride modules (HBGM) with reduced switch voltage stress is proposed in this paper. By using an auxiliary capacitor, a resonant circuit is formed to shape the current and voltage so that zero-voltage switching at turn-on instant is achieved. Since the switching loss dominates the power losses in a high-frequency dc–dc converter, the soft-switching performance leads to a noticeable reduction in the total loss; so, the operating temperature will decrease, and consequently, size of the heatsink will be reduced. The proposed circuit takes advantage of enhancement-mode gallium nitride (eGaN) switches regarding their small on-resistance RDS(on), low gate charge, and fast switching speed to improve both efficiency and power density. The main performance issue of adopting GaN switches in a bidirectional dc–dc converter is the high voltage stress of GaN devices, which is handled by connecting the HBGM in the active-clamped stacked configuration, as well as optimizing printed circuit board layout design. Finally, a 1 kW, 600 V laboratory prototype operating at 100 kHz is implemented to validate the proposed concept. [ABSTRACT FROM AUTHOR]

This paper introduces interleaved zero-current- transition (ZCT) converters where two sets of switches are operating out-of-phase and share the load power equally. Turn-on transitions at zero current and a significant reduction of the losses associated with diode reverse recovery are accomplished through addition of two small inductors. This paper describes a 30-kW (300 V/100 A) interleaved ZCT buck converter operating at 32-kHz effective switching frequency. Losses and efficiency of the experimental prototype compare favorably against the standard and interleaved hard-switched buck converters. Constant frequency operation with low switching losses and low output current ripple is very well suited for the realization of dc power supplies in plasma processes. [ABSTRACT FROM AUTHOR]

This paper deals with the development and implementation of a current-source-converter-based static synchronous compensator (CSC-STATCOM) applied to the volt-ampere- reactive (VAR) compensation problem of coal mining excavators. It is composed of a ±750-kVAR full-bridge CSC with selective harmonic elimination, a low-pass input filter tuned to 200 Hz, and a Δ/Y-connected coupling transformer for connection to medium-voltage load bus. Each power semiconductor switch is composed of an asymmetrical integrated gate commutated thyristor (IGCT) connected in series with a reverse-blocking diode and switched at 500 Hz to eliminate 5th, 7th, 11th, and 13th current harmonics produced by the CSC. Operating principles, power stage, design of dc link, and input filter are also described in this paper. It has been verified by field tests that the developed STATCOM follows rapid fluctuations in nearly symmetrical lagging and leading VAR consumption of electric excavators, resulting in nearly unity power factor on monthly basis, and the harmonic current spectra in the lines of CSC-STATCOM at the point of common coupling comply with the IEEE Std. 519-1992. [ABSTRACT FROM AUTHOR]